The present invention relates to a system for detecting the level of liquid in a tank, which is suitably used, for example, in detecting the level of fuel accumulated or accommodated in an automotive fuel tank.
Typically, as disclosed in JP-U 64-38534, the fuel tank mounted on the vehicle such as automobile is provided with a float-type level detecting system, for example, to detect the remaining amount of fuel accumulated in the tank. The float-type level detecting system comprises a float arranged vertically movably with the level of fuel accumulated in the fuel tank and a sensor part provided to the tank and for sensing a fuel level position in accordance with displacement of the float.
The float is coupled to an arm which is rotatable with respect to the sensor part. When fuel accumulated in the fuel tank increases or decreases, the float is vertically displaced with the liquid level in the tank, rotating the arm by an angle corresponding to that displacement.
The sensor part, which is in the form of a potentiometer or the like, comprises a resistor exposedly fixedly arranged in the fuel tank and a conductive slide brush which moves on the resistor in a sliding way when the arm rotates.
When a slide-contact position between the resistor and the slide brush varies with the angle of rotation of the arm, a value of resistance of the resistor varies accordingly. In accordance with this variation, the sensor part senses a position of the float, i.e. a fuel level position, which is announced as fuel remaining amount to a driver and the like.
With the typical level detecting system, the sensor part includes a potentiometer or the like to sense displacement of the float as displacement of a fuel level position.
However, the resistor of the sensor part is exposedly disposed in the fuel tank for slide contact with the slide brush of the arm. And the resistor and the slide brush are often immersed in fuel in the fuel tank.
As a result, with years of use of the level detecting system, the resistor and the slide brush can be subject to corrosion by various constituents and the like contained in fuel or cause contact failure, raising a problem of lowering the durability and reliability of the system.